app.css

:root {
    --color-text: #ffeeff;
    --color-neon: #ff00ff;
}

*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    font-family: 'Nunito', sans-serif;
    background: #262424;
    font-weight: 600;
    background: -moz-linear-gradient(top, #262424 0%, #110e0e 47%, #000000 100%);
    background: -webkit-linear-gradient(top, #262424 0%,#110e0e 47%,#000000 100%);
    background: linear-gradient(to bottom, #262424 0%,#110e0e 47%,#000000 100%);
    filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#262424', endColorstr='#000000',GradientType=0 );
    min-height: 100vh;
    display: grid;
    place-items: center;
}

.neon-button {
    font-size: 4rem;

    border: .1em solid var(--color-text);
    color: var(--color-text);
    display: inline-block;
    cursor: pointer;
    border-radius: .25em;
    text-decoration: none;
    box-shadow: 0 0 .75em 0 var(--color-neon),
        inset 0 0 .75em 0 var(--color-neon),
        0 0 .1em .05em var(--color-text),
        inset 0 0 .1em .05em var(--color-text);
    text-shadow: 0 0 .5em var(--color-neon),
        0 0 .1em var(--color-text);
    background: transparent;
    padding: .2em 1em;
    position: relative;
}

.neon-button::before {
    content: "";
    display: block;
    position: absolute;
    transition: opacity 50ms linear;
    top: 120%;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--color-neon);
    transform: perspective(1em) rotateX(45deg) scale(1, .35);
    filter: blur(1em);
    opacity: .5;
    pointer-events: none;
}

.neon-button::after {
    content: "";
    position: absolute;
    transition: opacity 50ms linear;
    top: -.1em;
    right: -.1em;
    bottom: -.1em;
    left: -.1em;
    border-radius: .25em;
    border: .1em solid var(--color-text);
    box-shadow: 0 0 2em .5em var(--color-neon),
        inset 0 0 1em 0 var(--color-neon);
    opacity: 0;
}

@keyframes blink {
    0% {
        color: inherit;
    }
    10% {
        color: inherit;
    }
    11% {
        color: black;
    }
    15% {
        color: black;
    }
    16% {
        color: inherit;
    }
    55% {
        color: inherit;
    }
    56% {
        color: black;
    }
    58% {
        color: black;
    }
    59% {
        color: inherit;
    }
    90% {
        color: inherit;
    }
    91% {
        color: black;
    }
    99% {
        color: black;
    }
    100% {
        color: inherit;
    }
}

.neon-button span, .neon-button span {
    animation: blink 2s linear infinite;
}

.neon-button:focus {
    outline: none;
}

.neon-button:hover::before, .neon-button:focus::before,
.neon-button:hover::after, .neon-button:focus::after {
    opacity: 1;
}